Cold expansion and reduction of thin-walled PVC tubes using a die

The production of sound thin-walled tubular parts by expansion and reduction using a die is generally limited to metals. Current research work in the field follows the same trend as that of industry and, therefore, there is no accumulated experience, no practical design rules and no information available in the specialized literature concerning the utilization of polyvinyl chloride (PVC) tubes (as well as other polymers). As far as authors are aware no technology validation studies have ever been performed with the objective of employing cold expansion and reduction forming processes for shaping the end of thin-walled PVC tubes. This paper is concerned with the abovementioned lack of knowledge and is a first step towards the understanding of the mechanics of deformation of tube end forming applied to PVC (and polymers, in general). The presentation addresses the influence of major process parameters on the formability limits of the expansion and reduction of thin-walled PVC tubes using a die and proposes an innovative extension of the flow formulation that is capable of modelling cold plastic deformation of pressure-sensitive polymers under a non-associated flow rule. The overall investigation is assessed with experimental data obtained under laboratory-controlled conditions and results show that free expansion and reduction of thin-walled PVC tubes using a die can be successfully utilized for producing custom and specific shapes at the tube ends.